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路由双向引入引发的环路与次优路径及解决方案

作者:互联网

验证理论:

1.逐步搭建双向路由引入,观察并分析路由表变化

  分析OSPF的两个不同优先级如何防止次优路径

2.引入外部150.1.1.1的路由,设计并分析存在的环路

3.破除环路的方案

  3.1修改优先级

  3.2修改cost

  3.3利用标签

3.破除次优路径的方案

 

 

实验拓扑:

 

 

 

 

初始配置:

配置接口及地址,OSPF及ISIS,不引入路由

初始结果:

[AR2]dis ip routing-table | in 150.1
150.1.2.2/32 Direct 0 0 D 127.0.0.1 LoopBack0

150.1.3.3/32 OSPF 10 1 D 155.1.23.3 GigabitEthernet0/0/1

 

[AR3]DIS IP routing-table | IN 150.1

150.1.2.2/32 OSPF 10 1 D 155.1.23.2 GigabitEthernet0/0/1
150.1.3.3/32 Direct 0 0 D 127.0.0.1 LoopBack0
150.1.4.4/32 ISIS-L2 15 20 D 10.1.35.5 GigabitEthernet0/0/0
150.1.5.5/32 ISIS-L2 15 10 D 10.1.35.5 GigabitEthernet0/0/0

 

[AR4]DIS IP routing-table | IN 150.1

150.1.2.2/32 OSPF 10 1 D 155.1.24.2 GigabitEthernet0/0/2
150.1.3.3/32 OSPF 10 2 D 155.1.24.2 GigabitEthernet0/0/2
150.1.4.4/32 Direct 0 0 D 127.0.0.1 LoopBack0
150.1.5.5/32 ISIS-L2 15 10 D 10.1.45.5 GigabitEthernet0/0/1

 

[AR5]dis ip routing-table | in 150.1

150.1.4.4/32 ISIS-L2 15 10 D 10.1.45.4 GigabitEthernet0/0/1
150.1.5.5/32 Direct 0 0 D 127.0.0.1 LoopBack0

 

 

 

一.

实验目的:

搭建路由双向引入

实验步骤:

第一步,在AR3上配置OSPE->ISIS的路由引入

[AR3]ip ip-prefix NET150 permit 150.1.0.0 16 less-equal 32 

[AR3-isis-1]filter-policy ip-prefix NET150 export 

[AR3-isis-1]import-route ospf 1 

此时AR2,3路由表不会变化,观察AR5,4路由表抉择

[AR5]DIS IP routing-table | IN 150.1

150.1.2.2/32 ISIS-L2 15 74 D 10.1.35.3 GigabitEthernet0/0/0
150.1.3.3/32 ISIS-L2 15 74 D 10.1.35.3 GigabitEthernet0/0/0
150.1.4.4/32 ISIS-L2 15 10 D 10.1.45.4 GigabitEthernet0/0/1
150.1.5.5/32 Direct 0 0 D 127.0.0.1 LoopBack0

        注解:外部引入到ISIS的路由开销默认64,类型为L2。本例中没有为ISIS接口配置任何开销值,ISIS接口的默认开销为10,开销类型为narrow

[AR4]dis ip routing-table | in 150.1

150.1.2.2/32 OSPF 10 1 D 155.1.24.2 GigabitEthernet0/0/2
150.1.3.3/32 OSPF 10 2 D 155.1.24.2 GigabitEthernet0/0/2
150.1.4.4/32 Direct 0 0 D 127.0.0.1 LoopBack0
150.1.5.5/32 ISIS-L2 15 10 D 10.1.45.5 GigabitEthernet0/0/1

 

[AR4]dis ip routing-table protocol isis | in 150.1

150.1.2.2/32 ISIS-L2 15 84 10.1.45.5 GigabitEthernet0/0/1
150.1.3.3/32 ISIS-L2 15 84 10.1.45.5 GigabitEthernet0/0/1

[AR4]dis ip routing-table protocol ospf | in 150.1

150.1.2.2/32 OSPF 10 1 D 155.1.24.2 GigabitEthernet0/0/2
150.1.3.3/32 OSPF 10 2 D 155.1.24.2 GigabitEthernet0/0/2

  注解:4.4和5.5的路由通过ISIS学到无可厚非。但是2.2和3.3在OSPF内部AR4是可以学到的,又因为2.2和3.3引入到了ISIS中,所以AR4作为边界路由器在ISIS中也可以学到2.2和3.3,此时根据协议优先级比较OSPF内部协议优先级10<ISIS优先级15,AR4选择155.1.24.2宣告的从OSPF学到的路由计入路由表

 

 

 

第二步,在AR3上配置ISIS->OSPF的引入,实现单点双向路由引入

已有:

[AR3]ip ip-prefix NET150 permit 150.1.0.0 16 less-equal 32 

[AR3-isis-1]filter-policy ip-prefix NET150 export 

[AR3-isis-1]import-route ospf 1 

再配:

[AR3-ospf-1]filter-policy ip-prefix NET150 export

[AR3-ospf-1]import-route isis 1

此时AR3,5路由表不会变化,观察AR2,4路由表抉择

[AR2]dis ip routing-table | in 150.1

150.1.2.2/32 Direct 0 0 D 127.0.0.1 LoopBack0
150.1.3.3/32 OSPF 10 1 D 155.1.23.3 GigabitEthernet0/0/1
150.1.4.4/32 O_ASE 150 1 D 155.1.23.3 GigabitEthernet0/0/1
150.1.5.5/32 O_ASE 150 1 D 155.1.23.3 GigabitEthernet0/0/1

  注释:AR2学习到从AR3过来的,通过路由引入的4,4和5.5的网段

[AR4]dis ip routing-table | in 150.1

150.1.2.2/32 OSPF 10 1 D 155.1.24.2 GigabitEthernet0/0/2
150.1.3.3/32 OSPF 10 2 D 155.1.24.2 GigabitEthernet0/0/2
150.1.4.4/32 Direct 0 0 D 127.0.0.1 LoopBack0
150.1.5.5/32 ISIS-L2 15 10 D 10.1.45.5 GigabitEthernet0/0/1

 

[AR4]dis ip routing-table protocol ospf | in 150.1

150.1.4.4/32 O_ASE 150 1 155.1.24.2 GigabitEthernet0/0/2
150.1.5.5/32 O_ASE 150 1 155.1.24.2 GigabitEthernet0/0/2

[AR4]dis ip routing-table protocol isis | in 150.1

150.1.5.5/32  ISIS-L2 15   10          D   10.1.45.5       GigabitEthernet0/0/1

4.4直连

  注释:AR4,5将自己的环回口路由,在AR3上传入OSPF中,AR3->AR2->AR4,AR4在OSPF外部路由中也学到了4.4和5.5,此时AR4比较协议优先级。发现OSPF外部路由优先级150>ISIS 15,所以AR4将来源于ISIS的4.4和5.5放入路由表中

 

 

 

第三步,在AR4上配置OSPF->ISIS引入

[AR4]ip ip-prefix NET150 permit 150.1.0.0 16 less-equal 32
[AR4-isis-1]filter-policy ip-prefix NET150 export
[AR4-isis-1]import-route ospf 1

此时AR2,4路由表不会变化,观察AR3,5路由表抉择

 [AR5]dis ip routing-table 

150.1.2.2/32 ISIS-L2 15 74 D 10.1.35.3 GigabitEthernet0/0/0
      ISIS-L2 15 74 D 10.1.45.4 GigabitEthernet0/0/1
150.1.3.3/32 ISIS-L2 15 74 D 10.1.35.3 GigabitEthernet0/0/0
      ISIS-L2 15 74 D 10.1.45.4 GigabitEthernet0/0/1
150.1.4.4/32 ISIS-L2 15 10 D 10.1.45.4 GigabitEthernet0/0/1
150.1.5.5/32 Direct 0 0 D 127.0.0.1 LoopBack0

  注释:AR5通过AR3,4都可以学习到2.2和3.3形成等价路由

 

[AR3]dis ip routing-table | in 150.1

150.1.2.2/32 OSPF 10 1 D 155.1.23.2 GigabitEthernet0/0/1
150.1.3.3/32 Direct 0 0 D 127.0.0.1 LoopBack0
150.1.4.4/32 ISIS-L2 15 20 D 10.1.35.5 GigabitEthernet0/0/0
150.1.5.5/32 ISIS-L2 15 10 D 10.1.35.5 GigabitEthernet0/0/0

 

[AR3]dis ip routing-table protocol  isis

150.1.2.2/32 ISIS-L2 15 84 10.1.35.5 GigabitEthernet0/0/0
150.1.3.3/32 ISIS-L2 15 84 10.1.35.5 GigabitEthernet0/0/0


[AR3]dis ip routing-table protocol ospf

150.1.2.2/32 OSPF 10 1 D 155.1.23.2 GigabitEthernet0/0/1

3.3直连

  注释:此时AR3在OSPF内部路由中学到2.2和3.3,同时由于AR4的引入,在ISIS中可以学到类型为ISIS L2的2.2和3.3.此时比较优先级,OSPF内部优先级10<ISIS 15所以在路由表中2.2和3.3为OSPF

 

 

第四步,在AR4上配置ISIS->OSPF引入

已有:

isis 1
is-level level-2
network-entity 49.0000.0000.0000.0000.0004.00
filter-policy ip-prefix NET150 export
import-route ospf 1

[AR4-ospf-1]dis ip ip-prefix
Prefix-list NET150
Permitted 4
Denied 5
index: 10 permit 150.1.0.0/16 ge 16 le 32

再配:

ospf 1
filter-policy ip-prefix NET150 export
import-route isis 1
area 0.0.0.0

此时AR4,5路由表不会变化,观察AR2,3路由抉择

[AR2]dis ip routing-table

150.1.2.2/32 Direct 0 0 D 127.0.0.1 LoopBack0
150.1.3.3/32 OSPF 10 1 D 155.1.23.3 GigabitEthernet0/0/1
150.1.4.4/32 O_ASE 150 1 D 155.1.23.3 GigabitEthernet0/0/1
      O_ASE 150 1 D 155.1.24.4 GigabitEthernet0/0/2
150.1.5.5/32 O_ASE 150 1 D 155.1.23.3 GigabitEthernet0/0/1
      O_ASE 150 1 D 155.1.24.4 GigabitEthernet0/0/2

  注释:AR2通过AR3,4都可以学习到4.4和5.5,形成等价路由

 

[AR3]dis ip routing-table | in 150.1

150.1.2.2/32 OSPF 10 1 D 155.1.23.2 GigabitEthernet0/0/1
150.1.3.3/32 Direct 0 0 D 127.0.0.1 LoopBack0
150.1.4.4/32 ISIS-L2 15 20 D 10.1.35.5 GigabitEthernet0/0/0
150.1.5.5/32 ISIS-L2 15 10 D 10.1.35.5 GigabitEthernet0/0/0


[AR3]dis ip routing-table protocol ospf | in 150.1

150.1.4.4/32 O_ASE 150 1 155.1.23.2 GigabitEthernet0/0/1
150.1.5.5/32 O_ASE 150 1 155.1.23.2 GigabitEthernet0/0/1

[AR3]dis ip routing-table protocol isis | in 150.1

150.1.4.4/32 ISIS-L2 15 20 D 10.1.35.5 GigabitEthernet0/0/0
150.1.5.5/32 ISIS-L2 15 10 D 10.1.35.5 GigabitEthernet0/0/0

  注释:此时AR3在ISIS内部学习到4.4,5.5的网段,同时4.4和5.5被AR4引入到OSPF中。此时AR3比较优先级。因为OSPF外部路由优先级150>ISIS 15所以4.4和5.5仍然选择ISIS路由学到的。

 

  因此,通过上面4个步骤发现,OSPF的两个不同优先级使得:路由器在OSPF内部学到的路由,优先于再从其他协议学到;路由器从其他协议(除BGP)直接学到的路由,优先于从OSPF里其他协议(除BGP)引入到OSPF的路由,从而实现次优路由的避免

 

 

 

 

 

 二.引入150.1.1.1,在AR3,4上设置,路由从ISIS引入到OSPF变为类型1

[AR1-ospf-1]import-route direct 

[AR3-ospf-1]import-route isis 1 type 1

[AR4-ospf-1]import-route isis 1 type 1 

  注释:OSPF type 1优先于type 2

分析:

假设150.1.1.1是先到AR3(因为AR1到达AR3和4是随机的),此时网络中存在逆时针环路AR3->AR2->AR4->AR5->AR3

    first           AR1将150.1.1.1的路由传到AR3,AR3将该路由引入到ISIS

    second     150.1.1.1经路由引入从AR3->AR5->AR4

    third          AR4比较从AR1->AR2->AR4学到的类型为OSPF的150.1.1.1/32和AR1->AR2->AR3(路由引入)->AR5->AR4学到的类型为ISIS的150.1.1.1/32.根据优先级比较,最后AR4上留下的是类型为ISIS的150.1.1.1/32

    fourth        因为AR4上存在有路由引入,于是将路由表中ISIS的150.1.1.1/32引入到OSPF中并且类型更改为1.此时AR2收到之后,对比从AR1收到的type 为2的150.1.1.1/32会认为从AR4上学习的type 为1的150.1.1.1/32是更优的。

    fifth    AR2将路由传递给AR3,此时AR3比较之前从AR2收到的type 2的150.1.1.1/32和现在从AR2收到的type 1的150.1.1.1/32同样会觉得后到的更优

    sixth     所以现在AR3认为要去150.1.1.1就去找AR2,AR2根据type比较去找AR4,AR4在ISIS中找到150.1.1.1的宣告者是AR3

 

假设150.1.1.1是先到的AR4(因为AR1到达AR3和4是随机的),此时网络中存在顺时针环路AR3->AR5->AR4->AR2->AR3

    first   AR1将150.1.1.1的路由传到AR4,AR4将此路由引入到ISIS

    second     150经路由引入从AR4->AR5->AR3

    third     AR3比较,认为从ISIS学到的150.1.1.1/32更优,计入路由表并

    fourth   AR3将ISIS的150.1.1.1/32引入到OSPF中更改类型为type 1.AR2收到之后认为从AR3上收到的type 为1的150.1.1.1/32更优

    fifth      AR2将路由传递给AR4,AR4通过比较同样认为从AR3学习的150.1.1.1/32更优

    sixth    所以现在AR4要去150.1.1.1就先在ISIS中找宣告者AR3,AR4认为经过AR2去AR3可以是去150.1.1.1的最优路径

 

验证:

在实验中AR1是先到了AR3(因为只有AR4上对于150.1.1.1是从ISIS学到的),此时网络中应存在逆时针环路

[AR3]dis ip routing-table 150.1.1.1

150.1.1.1/32 O_ASE 150 3 D 155.1.23.2 GigabitEthernet0/0/1

[AR4]dis ip routing-table 150.1.1.1

150.1.1.1/32 ISIS-L2 15 84 D 10.1.45.5 GigabitEthernet0/0/1

 

[AR3]tracert -a 150.1.3.3 150.1.1.1
traceroute to 150.1.1.1(150.1.1.1), max hops: 30 ,packet length: 40,press CTRL_C to break
1 155.1.23.2 30 ms 20 ms 20 ms
2 155.1.24.4 40 ms 30 ms 30 ms
3 10.1.45.5 50 ms 30 ms 30 ms
4 10.1.35.3 20 ms 20 ms 20 ms
5 155.1.23.2 40 ms 40 ms 30 ms
6 155.1.24.4 40 ms 30 ms 50 ms
7 10.1.45.5 40 ms 40 ms 40 ms
8 10.1.35.3 50 ms 40 ms 30 ms

[AR2]dis ospf routing

Routing for ASEs
Destination Cost Type Tag NextHop AdvRouter
150.1.1.1/32 2 Type1 1 155.1.23.3 10.1.35.3
150.1.4.4/32 2 Type1 1 155.1.23.3 10.1.35.3
150.1.4.4/32 2 Type1 1 155.1.24.4 10.1.45.4
150.1.5.5/32 2 Type1 1 155.1.23.3 10.1.35.3
150.1.5.5/32 2 Type1 1 155.1.24.4 10.1.45.4

 

 

 

三.破除环路的方案

3.1利用优先级破环

  在AR4上修改ISIS中收到的150.1.1.1的优先级为151,使得AR1->2->3->5->4时,在4上面类型为ISIS优先级变成151.所以AR4上会优选来自OSPF的优先级为150的150.1.1.1,所以在路由表中表现为OSPF,而不是被引入到OSPF中类型被改为level 1 从而破除

[AR4]ip ip-prefix NET0 permit 150.1.1.1 32 

[AR4-route-policy]if-match ip-prefix NET0

[AR4-route-policy]apply preference 151 

[AR4-isis-1]preference route-policy SET-PRI

[AR4]dis ip routing-table 150.1.1.1

150.1.1.1/32 O_ASE 150 3 D 155.1.24.2 GigabitEthernet0/0/2

此时逆时针的环被在AR4上止住。但是因为150.1.1.1在AR4上是OSPF的了,所以匹配上了OSPF->ISIS的引入。从AR4->AR5->AR3,在AR3上没有更改优先级,所以ISIS又以15的优先级打败了OSPF的150,所以在AR3上被引入到OSPF中,并更改为类型1了

再去查看AR3的路由

[AR3]dis ip routing-table 150.1.1.1

150.1.1.1/32 ISIS-L2 15 84 D 10.1.35.5 GigabitEthernet0/0/0

发现150.1.1.1是从ISIS学到的了,意味着又出现了顺时针的环路

[AR3]tracer -a 150.1.3.3 150.1.1.1
traceroute to 150.1.1.1(150.1.1.1), max hops: 30 ,packet length: 40,press CTRL_C to break
1 10.1.35.5 20 ms 10 ms 30 ms
2 10.1.45.4 20 ms 30 ms 20 ms
3 155.1.24.2 20 ms 30 ms 20 ms
4 155.1.23.3 10 ms 30 ms 20 ms
5 10.1.35.5 40 ms 30 ms 30 ms
6 10.1.45.4 40 ms 30 ms 40 ms
7 155.1.24.2 40 ms 30 ms 40 ms
8 155.1.23.3 30 ms 30 ms 30 ms

同样的解决思路,在AR3上将150.1.1.1/32的优先级更改为151

此时AR3,AR4的路由就都正常了,没有再通过路由引入使OSPF中出现type 1,环路破除

[AR3]ip ip-prefix NET1 permit 150.1.1.1 32 

[AR3]route-policy SET-PRE permit node 10
[AR3-route-policy]if-match ip-prefix NET1
[AR3-route-policy]apply preference 151

[AR3-isis-1]preference route-policy SET-PRE 

[AR3]dis ip routing-table 150.1.1.1

150.1.1.1/32 O_ASE 150 1 D 155.1.23.2 GigabitEthernet0/0/1

[AR4]dis ip routing-table 150.1.1.1

150.1.1.1/32 O_ASE 150 1 D 155.1.24.2 GigabitEthernet0/0/2

 

[AR4]tracert -a 150.1.4.4 150.1.1.1
traceroute to 150.1.1.1(150.1.1.1), max hops: 30 ,packet length: 40,press CTRL_C to break
1 155.1.24.2 20 ms 30 ms 30 ms
2 155.1.12.1 40 ms 40 ms 30 ms
[AR4]

 

 

 

3.2通过cost造环与破环

更改AR3,AR4上面的引入路由策略,取消引入时类型改为type 1 ,使他引入是就用默认的type 2。同时删除上面的优先级防环配置

此时查看AR3,4上的路由,发现AR4是ISIS,所以此次AR1是先到的AR3

[AR4]dis ip routing-table 150.1.1.1

150.1.1.1/32 ISIS-L2 15 84 D 10.1.45.5 GigabitEthernet0/0/1

[AR3]dis ip routing-table 150.1.1.1

150.1.1.1/32 O_ASE 150 1 D 155.1.23.2 GigabitEthernet0/0/1

当前网络中对于AR3上存在两条来自于AR2的等价路由:AR1->2->3->5->4(路由引入,默认type 2)->2->3还有AR1->AR2->AR3

[AR2]dis ip routing-table 150.1.1.1

150.1.1.1/32 O_ASE 150 1 D 155.1.12.1 GigabitEthernet0/0/0
      O_ASE 150 1 D 155.1.24.4 GigabitEthernet0/0/2

要创建环路,只需要配置cost使得AR2认为去AR1比去AR4远就可以了,所以修改AR2的g0/0/0接口开销为10

[AR2-GigabitEthernet0/0/0]OSPF cost 10

150.1.1.1/32 O_ASE 150 1 D 155.1.24.4 GigabitEthernet0/0/2

验证逆时针环路:

<AR3>tracert -a 150.1.3.3 150.1.1.1
traceroute to 150.1.1.1(150.1.1.1), max hops: 30 ,packet length: 40,press CTRL_C to break
1 155.1.23.2 20 ms 20 ms 20 ms
2 155.1.24.4 30 ms 40 ms 30 ms
3 10.1.45.5 30 ms 30 ms 30 ms
4 10.1.35.3 20 ms 30 ms 20 ms
5 155.1.23.2 30 ms 30 ms 30 ms
6 155.1.24.4 40 ms 50 ms 40 ms
7 10.1.45.5 40 ms 40 ms 50 ms
8 10.1.35.3 30 ms 30 ms 30 ms

 

破环:使得AR2认为去往AR1更近即可

删除AR2上g0/0/0口开销的配置,在AR2的g0/0/2口设置开销为10

[AR2-GigabitEthernet0/0/2]ospf cost 10

[AR3]tracert -a 150.1.3.3 150.1.1.1
traceroute to 150.1.1.1(150.1.1.1), max hops: 30 ,packet length: 40,press CTRL_C to break
1 155.1.23.2 30 ms 10 ms 20 ms
2 155.1.12.1 50 ms 30 ms 30 ms

路由:

 

 

[AR4]dis ip routing-table 150.1.1.1

150.1.1.1/32 ISIS-L2 15 84 D 10.1.45.5 GigabitEthernet0/0/1

 

 

同理,为了防止比如说设备重启了,当路由先到AR4产顺时针环路,此时AR2需要抉择去往AR1更近还是去往AR3更近。

为避免环路在AR2的g0/0/1口也设置ospf cost为10

[AR2-GigabitEthernet0/0/1]ospf cost 10

路由:

 

 

至此更改开销确实可以破环,但是无法解决次优路径的问题。

 

 

 

 

3.3通过标签

ISIS中如果要使用标签,必须使用开销类型为宽带,默认为窄带

删除上面的AR2的0/0/1和0/0/2的cost,增加g0/0/0的cost还原环路

<AR3>tracert -a 150.1.3.3 150.1.1.1
traceroute to 150.1.1.1(150.1.1.1), max hops: 30 ,packet length: 40,press CTRL_C to break
1 155.1.23.2 70 ms 10 ms 30 ms
2 155.1.24.4 20 ms 20 ms 20 ms
3 10.1.45.5 30 ms 40 ms 30 ms
4 10.1.35.3 70 ms 20 ms 20 ms
5 155.1.23.2 30 ms 30 ms 40 ms
6 155.1.24.4 40 ms 30 ms 30 ms
7 10.1.45.5 30 ms 30 ms 40 ms
8 10.1.35.3 30 ms 30 ms 20 ms

 

当前150.1.1.1是先到的AR3

[AR4]dis ip routing-table 150.1.1.1

150.1.1.1/32 ISIS-L2 15 84 D 10.1.45.5 GigabitEthernet0/0/1

[AR3]dis ip routing-table 150.1.1.1

150.1.1.1/32 O_ASE 150 1 D 155.1.23.2 GigabitEthernet0/0/1

 

原理:

  先更改AR3,4,5的开销类型为宽带

  在AR3上当OSPF->ISIS时将外部引入的路由(150.1.1.1,此时不使用前缀抓取,使得以后如果有其他外部路由引入也能匹配上这个策略路由)的路由打上TAG 3 ,在AR4上当ISIS->OSPF时将带了TAG 3 的路由deny掉,不允许再进入OSPF

配置:

AR3:

[AR3]route-policy OSPF->ISIS permit node 10 

[AR3-route-policy]if-match route-type external-type2

[AR3-route-policy]apply tag 3 

isis 1
is-level level-2
network-entity 49.0000.0000.0000.0000.0003.00
filter-policy ip-prefix NET150 export
import-route ospf 1 route-policy OSPF->ISIS

AR4:

 

[AR4]route-policy ISIS->OSPF deny node 10
[AR4-route-policy]if-match tag 3

ospf 1
filter-policy ip-prefix NET150 export
import-route isis 1 route-policy ISIS->OSPF
area 0.0.0.0

分析:

  此时路由走向:AR1->2->3->5->4,在AR4上不能被过滤到OSPF中,此时AR4比较从AR1->2->4发过来的优先级150的路由和AR1->2->3->5->4过来的优先级为15的路由,所以在AR4上150.1.1.1仍为ISIS路由,环路破除

[AR3]tracert -a 150.1.3.3 150.1.1.1
traceroute to 150.1.1.1(150.1.1.1), max hops: 30 ,packet length: 40,press CTRL_C to break
1 155.1.23.2 20 ms 20 ms 20 ms
2 155.1.12.1 20 ms 20 ms 40 ms
[AR3]

同理,为了防止比如说设备重启了,当路由先到AR4产顺时针环路,在AR4上当OSPF->ISIS设置外部引入的type 2 的路由打上标签4,在AR3上当ISIS->OSPF设置外部引入的路由上有标签4的都被丢掉

 

 

 

 

 

完整配置如下

AR3:

[AR3]dis route-policy
Route-policy : OSPF->ISIS
permit : 10 (matched counts: 1)
Match clauses :
if-match route-type external-type2
Apply clauses :
apply tag 3


Route-policy : ISIS->OSPF
deny : 10 (matched counts: 0)
Match clauses :
if-match tag 4
permit : 20 (matched counts: 4)
[AR3]isis
[AR3-isis-1]dis this
[V200R003C00]
#
isis 1
is-level level-2
network-entity 49.0000.0000.0000.0000.0003.00
filter-policy ip-prefix NET150 export
import-route ospf 1 route-policy OSPF->ISIS
#
return
[AR3-isis-1]ospf
[AR3-ospf-1]dis this
[V200R003C00]
#
ospf 1
filter-policy ip-prefix NET150 export
import-route isis 1 route-policy ISIS->OSPF
area 0.0.0.0
#
return
[AR3-ospf-1]

 

AR4:

[AR4]dis route-policy
Route-policy : ISIS->OSPF
deny : 10 (matched counts: 0)
Match clauses :
if-match tag 3
permit : 20 (matched counts: 5)


Route-policy : OSPF->ISIS
permit : 10 (matched counts: 0)
Match clauses :
if-match route-type external-type2
Apply clauses :
apply tag 4
[AR4]ospf
[AR4-ospf-1]dis this
[V200R003C00]
#
ospf 1
filter-policy ip-prefix NET150 export
import-route isis 1 route-policy ISIS->OSPF
area 0.0.0.0
#
return
[AR4-ospf-1]isis
[AR4-isis-1]dis this
[V200R003C00]
#
isis 1
is-level level-2
network-entity 49.0000.0000.0000.0000.0004.00
filter-policy ip-prefix NET150 export
import-route ospf 1 route-policy OSPF->ISIS
#
return
[AR4-isis-1]

 

此时,环路问题解决,但是次优路径仍然没有解决。解决方法看下一篇升级版,写不下了

标签:环路,AR3,ISIS,32,AR4,150.1,ms,次优,路由
来源: https://www.cnblogs.com/xiaohuihui4956/p/14861335.html